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Histology
Epithelial
- covering
Connective
- support
Muscle
- movement
Nervous
- control
- a sheet of cells that covers a body
surface or lines a body cavity
- forms the boundary between different
environments
- helps with protection, absorption,
filtration, excretion, secretion, and
sensory reception
-Avascular but innervated - no blood vessels diffusion nourishes the cells; nerve fibers
are present
-Regenerate quickly –
adequate nutrition = rapid cell division
-Cellularity – closely packed cells
-Specialized contacts - cells are linked by
tight junctions and desmosomes
Polarity- apical and basal surface cells differ in structure
and function
- apical surface- exposed to the body’s exterior or the
cavity of an internal organ
(microvilli = brush border, cilia)
- basal surface- interior surface; new cells arise from this
layer
- basal lamina- thin supporting sheet of glycoproteins
functions in diffusion and allows epithelial cells to
migrate to heal a wound
- reticular lamina- extracellular material containing
collagen protein fibers
The basement membrane (basal lamina and reticular
lamina) forms a boundary and reinforces the epithelial
sheet
Each Tissue Has a 2 Part Name
First Name = the number of cell layers present
Simple- single layer
(absorption and filtration)
Stratified- 2 or more layers
(protection)
Second = shape of cells
Squamous - flattened and scale-like
Cuboidal- boxlike; tall as they are wide
Columnar- tall and column shaped
cell layers can be different shapes, but are
named by the apical layer
cell layers can be different shapes, but are
named by the apical layer
cell layers can be different shapes, but are
named by the apical layer
Nuclear Shape and Placement
Squamous Cuboidal Columnar -
disc shaped
spherical
elongated top to bottom
and close to the cell
base
Simple Epithelial Functions
absorption, secretion and filtration
Simple Squamous- flattened, little cytoplasm, thin
Endothelium- slick, friction reduced lining.
Ex: heart, capillaries, lymphatic vessels
Mesothelium- found in serous membranes
lining the ventral cavity and its organs
Simple Cuboidal
Epitheliumsecretion & absorption
Ex: kidney tubules &
sm. ducts of glands
Simple Columnar
Epithelial Tissue
absoroption and secretion
Ex: digestive tract
dense microvilli for absorption
goblet cells- secrete a protective lubricating mucus
Pseudostratified Columnar Epithelium
- secretion and absorption
- cells vary in height, but all rest on the
basement membrane
Ex: respiratory tract
Stratified Squamous
Epithelial Tissue
-
widespread, thick, protection
top layer is squamous and deeper layers are
cuboidal or columnar
apical surface- keratinzed- rubbed away
Stratified Epithelia- mostly protection, basal cells
divide and push apically
Stratified Squamous Epithelium
Stratified Squamous
Epithelial Tissue
Stratified Columnar Epithelial Tissue
- rare - found in the lg. ducts of some glands
Transitional Epithelial Tissue
- cells are
able to
change
shape and
thin from 6
layers to 3
layers thick
- lines urinary
organs
Transitional Epithelial Tissue
A gland consists of 1 or more cells that make
and secrete a particular product.
Gland classification 2 distinctions
1. Site of product release
Endocrine- “internally secretion” release their product to the extra
cellular space
- ductless glands
- produce hormones that enter the blood or
lymphatic fluid
- very diverse group
Secretion
the product being released
the process of releasing the product
Exocrine- “external secretion” - send their
product to an epithelial surface inside or
outside the body
- secrete products onto body surfaces or in
body cavities (have ducts)
2.
Number of cells
Unicellular- scattered in epithelial sheets
goblet cells- produce mucin that
dissolves in water to make mucus
P 123
Multicellular- form by invagination or
evagination of an epithelial sheet
and most have ducts
2 parts to a multicellular gland: duct &
secretory unit
Ducts
Simple glands- single unbranched duct
Compound glands- branched duct
Simple
Compound
Secretory
Unit
tubular- secretory units form tubes
acinal or alveolar - secretory units form
small flask-like sacs
tubuloalveolar- contains both types of
secretory units
Merocrine glands- secrete
their products by exocytosis
Examples: pancreas, sweat
glands (most), salivary
glands
Holocrine glands- accumulate their
products then rupture releasing the
products and dead cell fragments
Example: sebaceous glands
Apocrine – accumulate their
products just under the cell
membrane then pinch off that
portion of the cell releasing
the secretory granules and
small amounts of cytoplasm
Ex: mammary glands
- most abundant and widely distributed tissue
- 4 main classes: connective tissue proper,
cartilage, bone and blood
- major functions: binding and support,
protection, insulation, transportation of
substances
- avascular to richly vascularized
- mostly non-living extracellular matrix
ground substance (matrix) - unstructured
material that fills the space between the
cells and contains the fibers
composed of interstitial fluid, cell adhesion
(glue) proteins and proteoglycans (protein
core with glycosaminoglycans attached)
3 types of fibers
- collagen fibers- tough, high tensile strength,
white fibers, cross linked bundles
- reticular fibers- fine collagenous fibers,
extensive branching, surround blood vessels
and support soft organ tissues
- elastic fibers- long, thin, form branching
networks, stretch and recoil because of
elastin, yellow fibers
Cells
- Clasts are cells that breakdown the matrix
- Blasts are immature cells that are actively mitotic
and secrete the ground substances and fibers
- Cytes mature cells are less active; They maintain
health of the matrix
connective tissue proper = fibroblast,
fibrocyte
cartilage = chondroblast, chondrocyte
bone = osteoblast, osteocyte, osteoclast
blood = hematopoietic stem cell
Other cells in the
connective tissue
WBC, plasma cells,
fat cells, mast cells,
macrophages
Plasma Cells – make antibodies
Mast Cells – inflammatory response
Macrophages – engulf foreign particles
Types of Connective Tissues
- major differences are cell type, fiber type and
the amounts
- all tissues are composed of living cells
surrounded by a matrix and arise from
mesenchyme tissue
- mesenchyme is the first tissue formed
from the mesoderm germ layer
Loose connective tissue (areolar, adipose, reticular)
Areolar- functions: support and binding other tissues,
hold body fluids, defend against infection,
store nutrients
- universal packing
material binding body
parts together yet
allowing them to move
freely over one another
Adipose - white fat
- high nutrient storing ability, large oil drop in center
- contains adipocytes (fat cells)
- closely packed cells that can’t divide
- shock absorber, insulation
- highly vascularized
- brown fat- baby fat
Reticular – (lymph nodes, spleen, bone marrow, liver)
only has reticular fibers in its matrix
forms a stroma that supports many blood cells
Dense Regular Connective Tissue - tendons,
ligaments
- closely packed bundles of collagen fibers
running in the same direction
- poorly vascularized
- tendons attach muscle
to bone
- ligaments attach bones
together
- aponeuroses- flat,
sheetlike tendons that
attach muscles to
other muscles or bones
Tendon
(cut longitudinally) The thick collagen fibers (pink) are lined up parallel to each other, in response to the
stress placed on them by muscle and joint action. Fibroblasts are squeezed between the fibers and
therefore also line up in parallel rows.
Dense Irregular Connective Tissue - (joint capsules,
dermis)
- able to withstand forces in multiple directions
- irregularly arranged collagen fibers with some
elastic fibers
Elastic
Connective Tissue
- large amounts
of elastic
fibers
Cartilage
- intermediate between bone and dense
connective tissue
- avascular and lacks nerve fiber
- large amounts of water and GAGs
- chondroblasts are the predominant cell
- chondrocytes (mature cartilage cells) are found
in cavities in small groups called lacunae
3 Types of Cartilage:
Hyaline, Elastic, Fibrocartilage
Hyaline cartilage or gristle
- most abundant cartilage type
- articular cartilage- springy pods in joints
- epiphyseal plates- (childhood) actively growing
regions near the ends of long bones
Elastic Cartilage (epiglottis and ear)
- like hyaline with more elastin fibers
- found where stretching is important
Fibrocartilage (knee and intervertebral discs)
- found where hyaline cartilage meets a ligament
or tendon
- provides strong support and withstands heavy
pressure rows of chondrocytes alternate with
rows of thick collagen fibers
Osseous Tissue
- support and protect body structures
- bones have cavities for fat storage and
synthesis of blood cells
- contains inorganic calcium salts in its matrix
- osteoblasts produce the organic portion of the
matrix
- vascularized
- osteocytes make lacunae to reside in
Blood
- blood cells surrounded by blood plasma
(matrix)
- fibers become visible only during clotting
- transport system for nutrients, wastes, gases
a continuous multicellular sheet composed at
least 2 primary tissue types- an epithelium
bound to an underlying layer of connective
tissue proper
4 membrane types
1. cutaneous membrane - skin
- keratinized stratified squamous
epithelium attached to thick dense
irregular connective tissue
2. mucous membranes or mucosae
- line body cavities that open to the exterior
- moist membranes
- the epithelial layer is underlain by a layer
of loose connective tissue = lamina propria
3. serous membranes or serosae
- moist membranes found in closed ventral
body cavities
- named according to their site and specific
organ associations
- produces thin, clear serous fluid that
lubricates the parietal and visceral layers
4. Synovial membrane
- Consists of modified connective tissue
- Produce hyaluronic acid for lubrication
- modified connective tissue
Nervous tissue contains 2 major cell types.
Neurons
-specialized branching cells that generate
and conduct nerve impulses
Supporting Cells
-non-conducting cells that support,
insulate, and protect neurons
Muscle Tissue
Characteristics
- highly cellular, well-vascularized
- responsible for most body movements
- possess myofilaments
3 types of muscle tissue
Muscle Tissue
Skeletal Muscle
Skeletal Muscle or Striated Muscle
- voluntary
- flesh of the body
- muscle fibers- long
cylindrical cells with many
nuclei and striations from
myofilaments
Muscle Tissue
Cardiac Muscle
-
found only in the heart
involuntary
striated, uninucleate
muscle fibersbranch with
unique junctions
called intercalated
discs
Muscle Tissue
Cardiac Muscle
Muscle Tissue
Smooth Muscle
- found in the digestive tract, uterus
- involuntary
- spindle shaped cells without striations and
a single nucleus
Muscle Tissue
Smooth Muscle
Muscle Tissue